Recalculation of scatter fractions for homogeneous and heterogeneous geometries using Geant4 Monte Carlo simulations
Bibliographic record
Abstract
The primary aim of this study was to determine the scatter fraction from patient, particularly in the presence of patient heterogeneities, using Monte Carlo simulations. The Geant4 toolkit was used to estimate the scatter fractions of 6, 10, 15, and 24 MV circular photon beams (area ~400 cm2). For scatter fraction calculation in a cubic water phantom at 100 cm from a point source, concentric spheres were designed, with the inner sphere radius ~1 m and the outer sphere was either 1.015 or 1.025 cm to allow dose build-up. The scatter fractions were calculated in water and heterogeneous medium (i.e. a slab of either lung, stainless steel, or aluminum) in the range of scattering angles (i.e. 3°-150°). Higher energy beams (i.e. 24 MV) exhibit a rapid fall-off in scatter fraction compared to lower energy beams (i.e. 6 MV). For angles below 35°, higher energy beams have the largest scatter fraction. Beyond 60°, smallest energy beams show the largest scatter fraction. The scatter fraction deviates by up to 48% from published data.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.004 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".